Antilipolytic Effect Research Articles

Chromium and Palmitic Acid Supplementation Modulate Adipose Tissue Insulin Sensitivity in Postpartum Dairy Cows

Periparturient dairy cows exhibit intense lipolysis driven by reduced dry matter intake, enhanced energy needs, and the loss of adipose tissue (AT) insulin sensitivity. Extended periods of low insulin sensitivity and negative energy balance induce lipolysis dysregulation, leading to increased disease susceptibility and poor lactation performance. Chromium (Cr) supplementation improves systemic insulin sensitivity, while palmitic acid (PA) increases energy availability for milk production. However, the effect of supplementing Cr and PA alone or in combination on insulin sensitivity in AT is unknown. Thirty-two multiparous cows were used in a randomized complete block design experiment and randomly assigned to one of 4 diets fed from 1 to 24 DIM. Diets included: control, no supplementation (CON, n = 8); Cr (Cr-propionate at 0.45 ppm Cr/kg DM, n = 8); PA (1.5% DM, n = 8); or Cr+PA (n = 8). Plasma samples were collected at -13 ± 5.1 d prepartum (PreP), and 14.4 ± 1.9d (PP1) and 21 ± 1.9d (PP2) after calving for albumin, BHB, BUN, calcium, cholesterol, glucose, nonesterified fatty acids (NEFA), total protein, iron, transferrin, triglycerides, and oxylipids quantification. Subcutaneous AT (SCAT) explants were collected at PreP, PP1 and PP2 and incubated in the presence of the lipolytic agent isoproterenol (ISO = 1 µM, BASAL = 0 µM) for 3 h. The antilipolytic effect of insulin (1µL/L) on SCAT explants was evaluated during ISO stimulation (IN+ISO). Lipolysis was quantified by glycerol release in the media (nmol glycerol/mg AT). Macrophage infiltration and adipocyte size were measured using hematoxylin and eosin-stained AT sections and immunohistochemistry. Cr tended to reduce postpartum NEFA concentrations when compared with CON, PA, and Cr+PA. Likewise, Cr increased the percentage of large adipocytes (>9000 µm2) postpartum compared with other diets. In line with higher lipid content, Cr-fed cows had higher ex-vivo BASAL lipolysis at PP2 when compared with PA and Cr+PA. ISO induced higher lipolysis at PP1 and PP2 but it was not affected by Cr and PA. IN+ISO reduced lipolysis by 29.91 ± 11% in Cr compared with ISO. In contrast, IN+ISO did not affect ISO lipolysis in CON, PA, and Cr+PA. Plasma transferrin was reduced by Cr. At PP2, PA cows had 3.3-fold higher macrophage infiltration in SCAT when compared with CON and Cr. Plasma 9-HODE and 9-oxoODE were increased by Cr+PA. PA increased plasma 13-oxoODE and Cr increased the ratio of 13-HODE:13-oxoODE. PA increased 5-iso Prostaglandin F2α-VI. Our results demonstrate that supplementing Cr during the immediate postpartum enhances SCAT insulin sensitivity and lipid accumulation. Further studies should determine the effects and mechanisms of action of Cr and PA on AT lipogenesis, adipogenesis, and their impact on lactation performance.

Metabolic Effects of Ketogenic Diets: Exploring Whole-Body Metabolism in Connection with Adipose Tissue and Other Metabolic Organs.

The ketogenic diet (KD) is characterized by minimal carbohydrate, moderate protein, and high fat intake, leading to ketosis. It is recognized for its efficiency in weight loss, metabolic health improvement, and various therapeutic interventions. The KD enhances glucose and lipid metabolism, reducing triglycerides and total cholesterol while increasing high-density lipoprotein levels and alleviating dyslipidemia. It significantly influences adipose tissue hormones, key contributors to systemic metabolism. Brown adipose tissue, essential for thermogenesis and lipid combustion, encounters modified UCP1 levels due to dietary factors, including the KD. UCP1 generates heat by uncoupling electron transport during ATP synthesis. Browning of the white adipose tissue elevates UCP1 levels in both white and brown adipose tissues, a phenomenon encouraged by the KD. Ketone oxidation depletes intermediates in the Krebs cycle, requiring anaplerotic substances, including glucose, glycogen, or amino acids, for metabolic efficiency. Methylation is essential in adipogenesis and the body's dietary responses, with DNA methylation of several genes linked to weight loss and ketosis. The KD stimulates FGF21, influencing metabolic stability via the UCP1 pathways. The KD induces a reduction in muscle mass, potentially involving anti-lipolytic effects and attenuating proteolysis in skeletal muscles. Additionally, the KD contributes to neuroprotection, possesses anti-inflammatory properties, and alters epigenetics. This review encapsulates the metabolic effects and signaling induced by the KD in adipose tissue and major metabolic organs.

SSTR2 Mediates the Inhibitory Effect of SST/CST on Lipolysis in Chicken Adipose Tissue.

Somatostatin shows an anti-lipolytic effect in both chickens and ducks. However, its molecular mediator remains to be identified. Here, we report that somatostatin type 2 receptor (SSTR2) is expressed at a high level in chicken adipose tissue. In cultured chicken adipose tissue, the inhibition of glucagon-stimulated lipolysis by somatostatin was blocked by an SSTR2 antagonist (CYN-154086), supporting an SSTR2-mediated anti-lipolytic effect. Furthermore, a significant pro-proliferative effect was detected in SST28-treated immortalized chicken preadipocytes (ICP-1), and this cell proliferative effect may be mediated through the MAPK/ERK signaling pathway activated by SSTR2. In summary, our results demonstrate that SSTR2 may regulate adipose tissue development by affecting the number and volume of adipocytes in chickens.

Sex differences in adipose insulin resistance are linked to obesity, lipolysis and insulin receptor substrate 1

Background/ObjectiveInsulin resistance is more prominent in men than women. If this involves adipose tissue is unknown and was presently examined.Subjects/MethodsAdipoIR (in vivo adipose insulin resistance index) was measured in 2344 women and 787 men. In 259 of the women and 54 of the men, insulin induced inhibition of lipolysis (acylglycerol breakdown) and stimulation of lipogenesis (glucose conversion to acylglycerols) were determined in subcutaneous adipocytes; in addition, basal (spontaneous) lipolysis was also determined in the fat cells. In 234 women and 115 men, RNAseq expression of canonical insulin signal genes were measured in subcutaneous adipose tissue. Messenger RNA transcripts of the most discriminant genes were quantified in 175 women and 109 men.ResultsMen had higher AdipoIR values than women but only when obesity (body mass index 30 kg/m2 or more) was present (p < 0.0001). The latter sex dimorphism was found among physically active and sedentary people, in those with and without cardiometabolic disease and in people using nicotine or not (p = 0.0003 or less). In obesity, adipocyte insulin sensitivity (half maximum effective hormone concentration) and maximal antilipolytic effect were tenfold and 10% lower, respectively, in men than women (p = 0.005 or less). Basal rate of lipolysis was two times higher in men than women (p > 0.0001). Sensitivity and maximum effect of insulin on lipogenesis were similar in both sexes (p = 0.26 and p = 0.18, respectively). When corrected for multiple comparison only RNAseq expression of insulin receptor substrate 1 (IRS1) was lower in men than women (p < 0.0001). The mRNA transcript for IRS1 was 60% higher in women than men (p < 0.0001).ConclusionsIn obesity, adipose tissue insulin resistance is more pronounced in men than in women. The mechanism involves less efficient insulin-mediated inhibition of adipocyte lipolysis, increased basal rate of lipolysis and decreased adipose expression of a key element of insulin signaling, IRS1.

Two Triterpenoids, ARM-2 and RA-5, From Protorhus longifolia Exhibit the Potential to Modulate Lipolysis and Lipogenesis in Cultured 3T3-L1 Adipocytes.

Triterpenoids have been identified as potential novel lipid-lowering drugs for the treatment of hypertriglyceridemia. This study investigated the potential antilipogenic and/or antilipolytic effects of two triterpenoids (ARM-2 and RA-5) isolated from the stem bark of Protorhus longifolia (Benrh.) Engl. Employing a combination of in silico predictions and in vitro assays, the interactions between these triterpenoids and key proteins involved in lipogenesis and lipolysis were investigated. In silico molecular docking analysis predicted a favourable binding affinity of both triterpenoids to PPARγ, SREBP-1, and AMPK, with lower binding affinity to C/EBPα, pancreatic lipase, and hormone-sensitive lipase (HSL). Both triterpenoids exhibited in vitro inhibition of pancreatic lipase with Ki and IC50 values ranging from 28.7 to 52.9 μM and 27.6 to 35.8 μM, respectively. Total and neutral lipid accumulation in differentiated 3T3-L1 adipocytes and the oleic acid-induced HepG2 cell model was inhibited, with ARM-2 showing better inhibition than RA-5. In the HepG2 model, the inhibitory activity of the two triterpenoids (at 25 and 100 μM) was comparable to 50 μM lovastatin, although the latter was cytotoxic, whereas both ARM-2 and RA-2 lacked cytotoxicity. Associated gene expression was similar to the effect of simvastatin where the expression of SREBP-1, PPARγ, C/EBPα, and HSL was reduced and that of AMPK was unchanged. In vitro studies confirmed that ARM-2 and RA-5 also inhibited adipocyte lipolysis, where the reduction in glycerol release by 25 and 100 μM was similar to 50 μM lovastatin and simvastatin. This study identifies that the triterpenoids, ARM-2 and RA-5, have the potential to modulate lipogenesis and lipolysis.

Insulin resistance in adipocytes: Novel insights into the pathophysiology of metabolic syndrome

Insulin resistance in all major target tissues is present in metabolic syndrome (MetS). The resistance in adipocytes is not well described and was presently examined. In this observational study on isolated abdominal white subcutaneous adipocytes from 419 adults, concentration-response effects of insulin on lipolysis inhibition (glycerol release) and lipogenesis stimulation (glucose conversion to total lipids) were determined. Insights into early and late insulin signaling events were obtained through the determination of insulin sensitivity (half maximum effective concentration) and responsiveness (maximum effect), respectively. In a subgroup of 132 subjects, we analyzed the subcutaneous adipose mRNA expression of genes in the canonical insulin signaling pathway using microarray. These results were validated using quantitative real-time polymerase chain reaction in 74 individuals. While the insulin responsiveness was similar in subjects with or without Mets, the sensitivity to insulin-mediated inhibition of lipolysis and stimulation of lipogenesis was ∼tenfold lower in subjects with MetS (p<0.0001). When age, sex, adipocyte volume, body mass index and body shape were considered, only the antilipolytic resistance was independently associated with MetS. The mRNA expression of several genes in the canonical insulin signaling pathway were altered in MetS (p<0.0006 or better) where the mRNA levels of insulin receptor substrate 2 associated with the antilipolytic effect (Rho=0.34; p=0.0016). The sensitivities of the antilipolytic and lipogenic effects of insulin are decreased in the MetS but only antilipolysis remains significant after multiple regression analysis. This resistance is localized at initial and receptor-near events in hormone signaling involving insulin receptor substrate 2.

Orthosteric ligand selectivity and allosteric probe dependence at Hydroxycarboxylic acid receptor HCAR2

Hydroxycarboxylic acid receptor 2 (HCAR2), a member of Class A G-protein-coupled receptor (GPCR) family, plays a pivotal role in anti-lipolytic and anti-inflammatory effects, establishing it as a significant therapeutic target for treating dyslipidemia and inflammatory diseases. However, the mechanism underlying the signaling of HCAR2 induced by various types of ligands remains elusive. In this study, we elucidate the cryo-electron microscopy (cryo-EM) structure of Gi-coupled HCAR2 in complex with a selective agonist, MK-6892, resolved to a resolution of 2.60 Å. Our structural analysis reveals that MK-6892 occupies not only the orthosteric binding pocket (OBP) but also an extended binding pocket (EBP) within HCAR2. Pharmacological assays conducted in this study demonstrate that the OBP is a critical determinant for ligand selectivity among the HCARs subfamily. Moreover, we investigate the pharmacological properties of the allosteric modulator compound 9n, revealing its probe-dependent behavior on HCAR2 in response to varying orthosteric agonists. Collectively, our findings provide invaluable structural insights that contribute to a deeper understanding of the regulatory mechanisms governing HCAR2 signaling transduction mediated by both orthosteric and allosteric ligands.

Effects of temperature-humidity index on blood metabolites of German dairy cows and their female calves

Heat stress (HS) impairs productivity, health, and welfare in dairy cows, and additionally causes metabolic changes. Hence, specific metabolites could be used as HS biomarkers. Consequently, the aim of the present study was to compare blood metabolite concentrations of German Holstein dairy cows and of their female calves suffering from high temperature-humidity index (THI) during late gestation (cows) or during their first week of life (calves) or not. According to the mean daily THI (mTHI) at the day before blood sampling, animals were classified into 2 groups: high mTHI ≥60 (hmTHI) and low mTHI <60 (lmTHI). To perform a standard cross-sectional 2-group study, cow groups (n = 48) and calf groups (n = 47) were compared separately. Differences in metabolite concentrations between hmTHI and lmTHI animals were inferred based on a targeted metabolomics approach. In the first step, processed metabolomics data were evaluated by multivariate data analysis techniques, and were visualized using the web-based platform MetaboAnalyst V5.0. The most important metabolites with pronounced differences between groups were further analyzed in a second step using linear mixed models. We identified 9 thermally sensitive metabolites for the cows [dodecanedioic acid; 3-indolepropionic acid; sarcosine; triglycerides (14:0_34:0), (16:0_38:7), (18:0_32:1), and (18:0_36:2); phosphatidylcholine aa C38:1; and lysophosphatidylcholine a C20:3] and for the calves [phosphatidylcholines aa C38:1, ae C38:3, ae C36:0, and ae C36:2; cholesteryl esters (17:1) and (20:3); sphingomyelins C18:0 and C18:1; and p-cresol sulfate], most of them related to lipid metabolism. Apart from 2 metabolites (3-indolepropionic acid and sarcosine) in cows, the metabolite plasma concentrations were lower in hmTHI than in lmTHI groups. In our heat-stressed dry cows, results indicate an altered lipid metabolism compared with lactating heat-stressed cows, due to the missing antilipolytic effect of HS. The results also indicate alterations in lipid metabolism of calves due to high mTHI in the first week of life. From a cross-generation perspective, high mTHI directly before calving seems to reduce colostrum quality, with detrimental effects on metabolite concentrations in offspring.

A new oral model of free fatty acid kinetics to assess lipolysis in subjects with and without type 2 diabetes.

Assessing free fatty acids (FFAs) kinetics and the role of insulin and glucose on FFA lipolysis and disposal may improve our understanding of the pathogenesis of type 2 diabetes (T2D). Some models have been proposed to describe FFA kinetics during an intravenous glucose tolerance test and only one during an oral glucose tolerance test. Here, we propose a model of FFA kinetics during a meal tolerance test and use it to assess possible differences in postprandial lipolysis in individuals with type 2 diabetes (T2D) and individuals with obesity without type 2 diabetes (ND). We studied 18 obese ND and 16 T2D undergoing three meal tolerance tests (MTT) on three occasions (breakfast, lunch, and dinner). We used plasma glucose, insulin, and FFA concentrations collected at breakfast to test a battery of models and selected the best one based on physiological plausibility, ability to fit the data, precision of parameter estimates, and the Akaike parsimony criterion. The best model assumes that the postprandial suppression of FFA lipolysis is proportional to the above basal insulin, while FFA disposal is proportional to FFA concentration. It was used to compare FFA kinetics in ND and T2D along the day. The maximum lipolysis suppression occurred significantly earlier in ND than T2D (39 ± 6 min vs. 102 ± 13 min, 36 ± 4 min vs. 78 ± 11 min, and 38 ± 6 min vs. 84 ± 13 min, P < 0.01, at breakfast, lunch, and dinner, respectively), making lipolysis significantly lower in ND than T2D. This is mainly attributable to the lower insulin concentration in the second group. This novel FFA model allows to assess lipolysis and insulin antilipolytic effect in postprandial conditions.NEW & NOTEWORTHY In this study, we propose a new mathematical model able to quantify postprandial FFA kinetics and adipose tissue insulin sensitivity in both subjects with obesity without type 2 diabetes (ND) and subjects with type 2 diabetes (T2D). Results show that the slower postprandial suppression of lipolysis in T2D contributes to the higher free fatty acid (FFA) concentration that, in turn, may contribute to hyperglycemia.

895-P: Effect of Long-Term Empagliflozin Therapy on Plasma Beta-Hydroxy Butyrate (ß-OHB)—Lack of Effect of Concomitant Insulin, GLP-1 Agonist, or Pioglitazone Therapy

Sodium-glucose transporter 2 (SGLT2) inhibitors are associated with increased risk of euglycemic diabetic ketoacidosis in T2DM. Possible mechanisms include increased lipolysis, elevated glucagon, and decreased plasma insulin levels. Therefore, concomitant high dose insulin as well as thiazolidinediones could potentially attenuate the rise in β-OHB because of anti-lipolytic effects. However, this has not been examined in the real-world clinical studies. We examined the effect of long-term Empagliflozin therapy on plasma β-OHB in veterans with T2DM. A retrospective chart review was performed in 43 subjects who had fasting β-OHB, C-peptide and detailed anthropometric measurements and were followed for 23 ± 2.5 months. Subjects were categorized into two groups based on fasting β-OHB concentrations (&amp;lt; or ≥2.8mg/dl). Eleven patients (24.4%) had high (6.03 ±1.22mg/dl) while 32 (74.6%) had normal β-OHB (1.42±0.09 mg/dL). There was no difference in age (59 ± 4 vs 62 ±2 yrs), BMI (35±1 vs 32 ±1 kg/m2), or the duration of diabetes (15 ± 3 vs 18±2 yrs) between the two groups. Subjects with higher β-OHB had higher HbA1c (8.9 ±0.7 vs 7.9 ± 0.3%, p&amp;lt;0.05). There was no difference in fasting C-peptide (3.2 ± 0.9 vs 3.5 ± 0.5ng/ml), total daily insulin dose (184± 43 vs 214±19 units/day), number of subjects on Pioglitazone (54 vs 35%) or GLP-1 agonist therapy (36 vs 52%) between the two groups. In conclusion, long-term therapy with Empagliflozin leads to elevated β-OHB in 25% of T2DM and it was associated with poor glycemic control. Concomitant insulin or pioglitazone therapy did not alter plasma β-OHB concentration. Disclosure L.C.Ortiz: None. J.Wortham: None. S.Pinkson: None. J.Trejo: None. A.S.Mendoza: None. X.Chen: None. D.Tripathy: None.

Effect of Crocetin on Basal Lipolysis in 3T3-L1 Adipocytes.

Crocetin (CCT) is a natural saffron-derived apocarotenoid that possesses healthy properties such as anti-adipogenic, anti-inflammatory, and antioxidant activities. Lipolysis is enhanced in obesity and correlates with a pro-inflammatory, pro-oxidant state. In this context, we aimed to investigate whether CCT affects lipolysis. To evaluate CCT's possible lipolytic effect, 3T3-L1 adipocytes were treated with CCT10μM at day 5 post-differentiation. Glycerol content and antioxidant activity were assessed using colorimetric assays. Gene expression was measured using qRT-PCR to evaluate the effect of CCT on key lipolytic enzymes and on nitric oxide synthase (NOS) expression. Total lipid accumulation was assessed using Oil Red O staining. CCT10μM decreased glycerol release from 3T3-L1 adipocytes and downregulated adipose tissue triglyceride lipase (ATGL) and perilipin-1, but not hormone-sensitive lipase (HSL), suggesting an anti-lipolytic effect. CCT increased catalase (CAT) and superoxide dismutase (SOD) activity, thus showing an antioxidant effect. In addition, CCT exhibited an anti-inflammatory profile, i.e., diminished inducible NOS (NOS2) and resistin expression, while enhanced the expression of adiponectin. CCT10μM also decreased intracellular fat and C/EBPα expression (a transcription factor involved in adipogenesis), thus revealing an anti-adipogenic effect. These findings point to CCT as a promising biocompound for improving lipid mobilisation in obesity.

An Artemisia scoparia extract attenuates glucocorticoid-induced lipolysis in adipocytes.

Prescription glucocorticoid (GC) use is widespread across developed countries for the treatment of several inflammatory conditions. Elevated GCs are known to promote lipolysis and metabolic disorders. An extract of Artemisia scoparia (SCO) has been shown to reduce lipolysis and promote metabolic health but has not been investigated in the context of excess GCs. Our aim was to examine the effects of SCO on GC-induced lipolysis. Mature adipocytes were pretreated with vehicle or SCO, then exposed to either the synthetic GC dexamethasone (DEX) or tumor necrosis factor alpha (TNFα). Medium was collected and assayed for glycerol and fatty acids as measures of lipolysis. The expression of several lipolytic genes and proteins was assessed, and the involvement of glucocorticoid receptor (GR) in SCO's effects was also interrogated. SCO significantly attenuated DEX-induced lipolysis but did not interfere with DEX-mediated changes in inflammatory gene profiles in adipocytes. SCO treatment resulted in significant reductions in monomeric phosphodiesterase (PDE) protein levels while elevating PDE multimeric complex formation, but other canonical lipolytic mediators were unaltered. SCO attenuated lipolysis even when GR expression was significantly knocked down. Finally, it was demonstrated that SCO was distinct from rosiglitazone in its antilipolytic effects. SCO attenuates GC-induced lipolysis independently of GR activity. Future studies are needed to elucidate underlying mechanisms.

An allosteric modulator of the adenosine A1 receptor potentiates the antilipolytic effect in rat adipose tissue

The adenosine A1 receptor plays important roles in tuning free fatty acid (FFA) levels and represents an attractive target for metabolic disorders. Though remarkable progress has been achieved in the exploitation of effective (orthosteric) A1 receptor agonists in modulating aberrant FFA levels, the effect of A1 receptor allosteric modulation on lipid homeostasis is less investigated. Herein we sought to explore the effect of an allosteric modulator on the action of an A1 receptor orthosteric agonist in regulating the lipolytic process in vitro and in vivo. We examined the binding kinetics of a selective A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (CCPA) in the absence or presence of an allosteric modulator (2-amino-4,5-dimethyl-3-thienyl)-[3-(trifluoromethyl)-phenyl]methanone (PD81,723) on rat adipocyte membranes. We also examined the allosteric effects of PD81,723 on mediating the CCPA-induced inhibition of cAMP accumulation, HSL (hormone-sensitive lipase) phosphorylation and FFA production in in vitro and in vivo models. Our results demonstrated that PD81,723 slowed down the dissociation of CCPA from the A1 receptor, which, consequently, potentiated the antilipolytic action of CCPA through downregulating the cAMP/HSL pathway. Our study exemplified the application of A1 receptor allosteric modulators as an alternative for metabolic disease treatments.

Oleic acid abomasal infusion limits lipolysis and improves insulin sensitivity in adipose tissue from periparturient dairy cows

Excessive adipose tissue (AT) lipolysis around parturition in dairy cows is associated with impaired AT insulin sensitivity and increased incidence of metabolic diseases. Supplementing cows with oleic acid (OA) reduces circulating biomarkers of lipolysis and improves energy balance. Nevertheless, it is unclear if OA alters lipid trafficking in AT. In the liver and skeletal muscle, OA improves mitochondrial function and promotes lipid droplet formation by activating perilipin 5 (PLIN5) and peroxisome proliferator-activated receptor α (PPARα). However, it is unknown if this mechanism occurs in AT. The objective of this study was to determine the effect of OA on AT lipolysis, systemic and AT insulin sensitivity, and AT mitochondrial function in periparturient dairy cows. Twelve rumen-cannulated Holstein cows were infused abomasally following parturition with ethanol (CON) or OA (60 g/d) for 14 d. Subcutaneous AT samples were collected at 11 ± 3.6 d before calving (-12 d), and 6 ± 1.0 d (7 d) and 13 ± 1.4 d (14 d) after parturition. An intravenous glucose tolerance test was performed on d 14. Adipocyte morphometry was performed on hematoxylin and eosin-stained AT sections. The antilipolytic effect of insulin (1 μg/L) was evaluated using an ex vivo explant culture following lipolysis stimulation. PLIN5 and PPARα transcription and translation were determined by real-time quantitative PCR and capillary electrophoresis, respectively. RNA sequencing was used to evaluate the transcriptomic profile of mitochondrial gene networks. In CON cows, postpartum lipolysis increased the percentage of smaller (<3,000 µm2) adipocytes at 14 d compared with -12 d. However, OA limited adipocyte size reduction at 14 d. Likewise, OA decreased lipolysis plasma markers nonesterified free fatty acids and β-hydroxybutyrate at 5 and 7 d. Over the 14-d period, compared with CON, OA increased the concentration of plasma insulin and decreased plasma glucose. During the glucose tolerance test, OA decreased circulating glucose concentration (at 10, 20, 30, 40 min) and the glucose clearance rate. Moreover, OA increased insulin at 10 and 20 min and tended to increase it at 30 min. Following lipolysis stimulation, OA improved the antilipolytic effect of insulin in the AT at 14 d. PLIN5 and PPARA gene expression decreased postpartum regardless of treatment. However, OA increased PLIN5 protein expression at 14 d and increased PPARA at 7 and 14 d. Immunohistochemical analysis of AT and RNA sequencing data showed that OA increased the number of mitochondria and improved mitochondrial function. However, OA had no effect on production and digestibility. Our results demonstrate that OA limits AT lipolysis, improves systemic and AT insulin sensitivity, and is associated with markers of mitochondrial function supporting a shift to lipogenesis in AT of periparturient dairy cows.

The anxiolytic drug opipramol inhibits insulin-induced lipogenesis in fat cells and insulin secretion in pancreatic islets.

The antidepressant drug opipramol has been reported to exert antilipolytic effect in human adipocytes, suggesting that alongside its neuropharmacological properties, this agent might modulate lipid utilization by peripheral tissues. However, patients treated for depression or anxiety disorders by this tricyclic compound do not exhibit the body weight gain or the glucose tolerance alterations observed with various other antidepressant or antipsychotic agents such as amitriptyline and olanzapine, respectively. To examine whether opipramol reproduces or impairs other actions of insulin, its direct effects on glucose transport, lipogenesis and lipolysis were investigated in adipocytes while its influence on insulin secretion was studied in pancreatic islets. In mouse and rat adipocytes, opipramol did not activate triglyceride breakdown, but partially inhibited the lipolytic action of isoprenaline or forskolin, especially in the 10-100 μM range. At 100 μM, opipramol also inhibited the glucose incorporation into lipids without limiting the glucose transport in mouse adipocytes. In pancreatic islets, opipramol acutely impaired the stimulation of insulin secretion by various activators (high glucose, high potassium, forskolin...). Similar inhibitory effects were observed in mouse and rat pancreatic islets and were reproduced with 100 μM haloperidol, in a manner that was independent from alpha2-adrenoceptor activation but sensitive to Ca2+ release. All these results indicated that the anxiolytic drug opipramol is not only active in central nervous system but also in multiple peripheral tissues and endocrine organs. Due to its capacity to modulate the lipid and carbohydrate metabolisms, opipramol deserves further studies in order to explore its therapeutic potential for the treatment of obese and diabetic states.

Pregnancy but Not Moderate Undernutrition Attenuates Insulin Suppression of Fat Mobilization in Sheep , ,

Nonpregnant and late-pregnant ditocous ewes were fed either to maintain zero energy balance in maternal tissues (fed) or at 50% of this level (underfed) for several weeks. Plasma concentrations of nonesterified fatty acids (NEFA) and glycerol were measured under basal conditions and during infusion of various doses of insulin while maintaining euglycemia (hyperinsulinemic, euglycemic clamp technique). Pregnancy and undernutrition separately increased basal plasma NEFA concentration in an additive manner; plasma glycerol was increased by pregnancy but unaffected by undernutrition. The molar ratio of NEFA to glycerol was significantly greater in underfed ewes. Analysis of dose-response relations between plasma insulin and metabolites during insulin infusions showed that maximally insulin-suppressed concentrations of NEFA and glycerol were significantly greater in pregnant than in nonpregnant ewes but were unaffected by undernutrition. Neither pregnancy nor undernutrition affected the maximally insulin-suppressed NEFA to glycerol ratio, or the plasma insulin concentration for 50% maximal responses to insulin of plasma NEFA, plasma glycerol, or the plasma NEFA to glycerol ratio. Thus, even in ewes at or close to zero energy balance, pregnancy seems to reduce adipose responsiveness but not sensitivity to the antilipolytic effect of insulin. This is another manifestation of the normal development of insulin resistance in maternal tissues during late pregnancy.

Glucose-Induced Hemodynamic and Metabolic Response of Skeletal Muscle in Heart Failure Patients with Reduced vs. Preserved Ejection Fraction-A Pilot Study.

(1) Background: Insulin resistance (IR) is a characteristic pathophysiologic feature in heart failure (HF). We tested the hypothesis that skeletal muscle metabolism is differently impaired in patients with reduced (HFrEF) vs. preserved (HFpEF) ejection fraction. (2) Methods: carbohydrate and lipid metabolism was studied in situ by intramuscular microdialysis in patients with HFrEF (59 ± 14y, NYHA I-III) and HFpEF (65 ± 10y, NYHA I-II) vs. healthy subjects of similar age during the oral glucose load (oGL); (3) Results: There were no difference in fasting serum and interstitial parameters between the groups. Blood and dialysate glucose increased significantly in HFpEF vs. HFrEF and controls upon oGT (both p &lt; 0.0001), while insulin increased significantly in HFrEF vs. HFpEF and controls (p &lt; 0.0005). Muscle tissue perfusion tended to be lower in HFrEF vs. HFpEF and controls after the oGL (p = 0.057). There were no differences in postprandial increases in dialysate lactate and pyruvate. Postprandial dialysate glycerol was higher in HFpEF vs. HFrEF and controls upon oGL (p = 0.0016); (4) Conclusion: A pattern of muscle glucose metabolism is distinctly different in patients with HFrEF vs. HFpEF. While postprandial IR was characterized by impaired tissue perfusion and higher compensatory insulin secretion in HFrEF, reduced muscle glucose uptake and a blunted antilipolytic effect of insulin were found in HFpEF.

Relationship Between a Sedentary Lifestyle and Adipose Insulin Resistance.

Sedentary people have insulin resistance in their skeletal muscle, but whether this also occurs in fat cells was unknown. Insulin inhibition of hydrolysis of triglycerides (antilipolysis) and stimulation of triglyceride formation (lipogenesis) were investigated in subcutaneous fat cells from 204 sedentary and 336 physically active subjects. Insulin responsiveness (maximum hormone effect) and sensitivity (half-maximal effective concentration) were determined. In 69 women, hyperinsulinemia-induced circulating fatty acid levels were measured. In 128 women, adipose gene expression was analyzed. Responsiveness of insulin for antilipolysis (60% inhibition) and lipogenesis (twofold stimulation) were similar between sedentary and active subjects. Sensitivity for both measures decreased ˜10-fold in sedentary subjects (P < 0.01). However, upon multiple regression analysis, only the association between antilipolysis sensitivity and physical activity remained significant when adjusting for BMI, age, sex, waist-to-hip ratio, fat-cell size, and cardiometabolic disorders. Fatty acid levels decreased following hyperinsulinemia but remained higher in sedentary compared with active women (P = 0.01). mRNA expression of insulin receptor and its substrates 1 and 2 was decreased in sedentary subjects. In conclusion, while the maximum effect is preserved, sensitivity to insulin's antilipolytic effect in subcutaneous fat cells is selectively lower in sedentary subjects.

Exploring GPR109A Receptor Interaction with Hippuric Acid Using MD Simulations and CD Spectroscopy

Previous research has indicated that various metabolites belonging to phenolic acids (PAs), produced by gut microflora through the breakdown of polyphenols, help in promoting bone development and protecting bone from degeneration. Results have also suggested that G-protein-coupled receptor 109A (GPR109A) functions as a receptor for those specific PAs such as hippuric acid (HA) and 3-(3-hydroxyphenyl) propionic acid (3-3-PPA). Indeed, HA has a molecular structural similarity with nicotinic acid (niacin) which has been shown previously to bind to GPR109A receptor and to mediate antilipolytic effects; however, the binding pocket and the structural nature of the interaction remain to be recognized. In the present study, we employed a computational strategy to elucidate the molecular structural determinants of HA binding to GPR109A and GPR109B homology models in understanding the regulation of osteoclastogenesis. Based on the docking and molecular dynamics simulation studies, HA binds to GPR109A similarly to niacin. Specifically, the transmembrane helices 3, 4 and 6 (TMH3, TMH4 and TMH6) and Extracellular loop 1 and 2 (ECL1 and ECL2) residues of GRP109A; R111 (TMH3), K166 (TMH4), ECL2 residues; S178 and S179, and R251 (TMH6), and residues of GPR109B; Y87, Y86, S91 (ECL1) and C177 (ECL2) contribute for HA binding. Simulations and Molecular Mechanics Poisson-Boltzmann solvent accessible area (MM-PBSA) calculations reveal that HA has higher affinity for GPR109A than for GPR109B. Additionally, in silico mutation analysis of key residues have disrupted the binding and HA exited out from the GPR109A protein. Furthermore, measurements of time-resolved circular dichroism spectra revealed that there are no major conformational changes in the protein secondary structure on HA binding. Taken together, our findings suggest a mechanism of interaction of HA with both GPR109A and GPR109B receptors.

Lpcat3 deficiency promotes palmitic acid-induced 3T3-L1 mature adipocyte inflammation through enhanced ROS generation.

Phosphatidylcholines (PCs) are major phospholipids in the mammalian cell membrane. Structural remodeling of PCs is associated with many biological processes. Lysophosphatidylcholine acyltransferase 3 (Lpcat3), which catalyzes the incorporation of polyunsaturated fatty acyl chains into the sn-2 site of PCs, plays an important role in maintaining plasma membrane fluidity. Adipose tissue is one of the main distribution organs of Lpcat3, while the relationship between Lpcat3 and adipose tissue dysfunction during overexpansion remains unknown. In this study, we reveal that both polyunsaturated PC content and Lpcat3 expression are increased in abdominal adipose tissues of high-fat diet-fed mice when compared with chow-diet-fed mice, indicating that Lpcat3 is involved in adipose tissue overexpansion and dysfunction. Our experiments in 3T3-L1 adipocytes show that inhibition of Lpcat3 does not change triglyceride accumulation but increases palmitic acid-induced inflammation and lipolysis. Conversely, Lpcat3 overexpression exhibits anti-inflammatory and anti-lipolytic effects. Furthermore, mechanistic studies demonstrate that Lpcat3 deficiency promotes reactive oxygen species (ROS) generation by increasing NOX enzyme activity by facilitating the translocation of NOX4 to lipid rafts, thereby aggregating 3T3-L1 adipocyte inflammation induced by palmitic acid. Moreover, overexpression of Lpcat3 exhibits the opposite effects. These findings suggest that Lpcat3 protects adipocytes from inflammation during adipose tissue overexpansion by reducing ROS generation. In conclusion, our study demonstrates that Lpcat3 deficiency promotes palmitic acid-induced inflammation in 3T3-L1 adipocytes by enhancing ROS generation.